Code Division Multiple Access (CDMA)/Wideband Code Division Multiple Access (WCDMA) is the 3rd generation communication standard, which meets the high speed data transmission. In the CDMA/WCDMA system, the mobile phone is powered entirely depending on the battery. In order to meet the strict linear index and Adjacent Channel Power Ratio (ACPR) index defined in the IS95/3GPP spread spectrum standard, the mobile phone needs to adopt class A or class AB Radio Frequency (RF) power amplifier with high linearity. FIG. 1 is a schematic diagram of the typical RF power amplifier of the mobile phone in the CDMA/WCDMA system, and as shown in FIG. 1, the RF power amplifier needs two channels of supply voltages which are Vref and Vcc, wherein Vref provides the bias for the base of the power amplifier and Vcc provides the bias for the collector of the power amplifier, both the base bias voltage Vref and the collector bias voltage Vcc are constant values. When the max RF output power Po=28 dBm, the efficiency of this class of the RF power amplifier (RF power amplifier E) is just 35%, and when the RF output power is lower, the efficiency is lower. In practical applications, when in a speech mode, the RF power amplifier works in a continuous mode, that is because the working time of the mobile phone is 50% or ⅛ when the user is not in a call, and therefore, it is unnecessary to consider the heating problem of the mobile phone in the speech mode, however, in the data mode, the RF power amplifier keeps in a continuous working state all the time before ending the data transmission, the lower efficiency of the RF power amplifier and the continuous working state of RF power amplifier will consume a lot of battery capacity, and the internal power consumption produced by the consuming the battery capacity will make the mobile phone overheat.